Southland lakes mirror national results
The water quality in Southland lakes reflects the national picture, with lowland lakes tending to have poor water quality and lakes in upland areas more likely to have good water quality.
The national results were released today (26/12/20) by LAWA (Land, Air, Water Aotearoa) in its first lake water quality national picture summary.
The data for the national picture was provided to LAWA by regional and unitary councils and analysed by a science team that included Cawthron Institute. Analysis was based on the Trophic Level Index (TLI), which combines several indicators to determine overall lake condition. Of New Zealand’s 3800-odd lakes, 124 are being monitored regularly.
Environment Southland science manager Dr Elaine Moriarty said the results were to be expected.
“We typically see poorer water quality in areas that have been highly developed or modified by humans, so this is not a surprise. These are the areas where we often focus our monitoring too, so that we can understand the impact.”
Southland has almost 1000 lakes, including several large, iconic lakes that are valued highly by people for aesthetic, cultural, recreational and economic reasons. Most Southland lakes are in Fiordland. Fiordland lakes are considered to have pristine water quality as their catchments are native bush. Lake Manapouri and Lake Te Anau are the two Fiordland lakes monitored monthly within Environment Southland’s sampling programme.
The Council regularly monitors seven lakes in Southland and the data from our monitoring was factored into LAWA’S national picture.
The seven lakes include three lowland lakes – Lake George, the Reservoir and Lake Vincent – which have poor or very poor water quality; two brackish lakes (those that have salt water and freshwater) – Waiau Lagoon and Waituna Lagoon – which have poor water quality; and two deep lakes – Lake Te Anau and Lake Manapouri – which have very good water quality. Go to www.LAWA.org.nz to see information on the monitored Southland lakes.
Improving water quality in Southland is the Council’s top priority and our People, Water and Land programme is focused on regulatory and non-regulatory methods to achieve this. Additionally, we are part of a proactive multi-agency partnership to restore the health of and wellbeing of Waituna Lagoon, the catchment and its community.
People wanting to swim in lakes need to assess the situation before getting in. If a lake has a poor Trophic Level Index rating it usually means more algae growth and a higher risk of toxic algae blooms. It is not safe for people to swim during a bloom.
“While the regional council monitors for blooms, we can’t monitor everywhere. Signs of toxic algae in lakes are a ‘pea soup’ consistency and cloudy water with small green blobs. This is different to the toxic algae found in rivers, which presents as green/brown slime on rocks, or dark bown/black mats on the water’s edge,” said Dr Moriarty.
Other tips for swimming in either lakes or rivers include not doing so within 48 hours of heavy rainfall, ensuring you can see your toes when you stand knee deep in the water and checking that it doesn’t smell bad.
LAWA has a special ‘can I swim here?’ section on its website to help people make good decisions on where to swim throughout the country: https://www.lawa.org.nz/explore-data/swimming/
